Municipal solid waste (“MSW”) is the gross product collected and processed by municipalities and governments. MSW includes durable and non-durable goods, containers and packaging, food and yard wastes, as well as miscellaneous inorganic wastes from residential, commercial, and industrial sources. Examples include newsprint, appliances, clothing, scrap food, containers and packaging, disposable diapers, plastics of all sort including disposable tableware and foamed packaging materials, rubber and wood products, potting soil, yard trimmings and consumer electronics, as part of an open-ended list of disposable or throw-away products. A traditional method of waste disposal is a landfill, which is still a common practice in some areas. Many local authorities, however, have found it difficult to establish new landfills. In those areas, the solid waste must be transported for disposal, making it more expensive.
As an alternative to landfills, a substantial amount of MSW may be disposed of by combustion at a municipal solid waste combustor (“MWC”) to help recover energy from the waste. The conversion of waste to energy is often performed at a waste-to-energy plant (“WTE”). One of the problems associated with the conventional combustion of MSW and other solid fuels is that it creates small amounts of undesirable and potentially harmful byproducts, such as NOx, carbon monoxide, and dioxins. For example, NOx is formed during combustion through two primary mechanisms. First, fuel NOx is formed by the oxidation of organically bound nitrogen (N) found in MSW and other fuels. When the amount of O2 in the combustion chamber is low, N2 is the predominant reaction product. However, when a substantial amount of O2 is available, an increased portion of the fuel-bound N is converted to NOx. Second, thermal NOx is formed by the oxidation of atmospheric N2 at high temperatures. Because of the high activation energy required, thermal NOx formation does not become significant until flame temperatures reach 1,100° C. (2,000° F.).
Despite the improvements made in reducing the harmful emissions of conventional combustion systems, there is still a need for alternative methods and systems that efficiently convert MSW or other solid fuels to energy while producing a minimal amount of undesirable emissions.